JPH0447273Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a safety device for an earth drill that is configured to be usable as a crane and is equipped with an overload prevention device for a crane.

(Prior art) Fig. 4 shows a structure that can be used as a crane.
This earth drill is an example of an earth drill equipped with an overload prevention device for a crane.
c is installed, and a hydraulic cylinder 3 is installed on the upper revolving body 1c.
The telescoping boom 2 is attached so that it can be raised and lowered freely, and the Kelly rope 7 wound around the hoisting winch 9 installed on the upper revolving structure 1c is attached to the sheave 4 at the top of the boom 2.
0,41, and connect the Kelly bar 6 to the lower end of the Kelly rope 7 via the swivel joint 42.
Earth drill bucket 10 is attached to the bottom end of Kellyba 6.
is installed. The kelly bar 6 has a rectangular cross section and is inserted into a square hole of the rotating body of the kelly bar drive device 5 at the end of the front frame 4. 43, it is attached by a pin 45 so that it can be raised and lowered freely by a luffing device 44 consisting of a winch, and can be attached and detached together with the Kerry bar drive device 5 and the luffing device 44. The Kelly bar drive device 5 is supported by the boom 2 via a hanging rope 8.

In addition, when using the hoisting winch 9 as a crane using an auxiliary hoisting winch (not shown) installed in parallel with the hoisting winch 9 during earth drilling work, the hoisting device 4
The front frame 4 is held in by winding the winch 4, and hooks are attached to the tips of auxiliary winding ropes (not shown) hung around the sheaves 40 and 41, and crane work is performed. In order to make this possible, two or more sheaves 40, 41 are coaxially provided on the top of the boom 2, for example, the right sheave 40, 41 is provided with a Kelly rope 7, and the left sheave 40, 41 is provided with a supplementary rope. A winding rope can be hung.

Additionally, if necessary, a bracket having a sheave (none of which is shown) may be attached to the top of the boom 2, and the auxiliary hoisting rope wound around the auxiliary hoisting winch may be hung on the sheave to perform crane work. There is also.

Furthermore, this earth drill may be used as a crane by removing the front frame 4 together with the Kelly bar drive device 5 and the hoisting device 44, and passing the main winding rope between the sheave 41 and a hook block (not shown).

In addition, this earth drill has an overload prevention device in order to prevent overload during crane work, and as an input device for the overload prevention device, a load detection device is installed between the boom 2 and the boom 2 hydraulic cylinder 3. 11 (there is also a type of load detector that detects rope tension), a boom angle detector 12 provided at the base of the boom 2, and a boom length detector 13. In addition, in order to detect overwinding of the Kelly rope (main winding rope) 7, an overwinding weight 14 is engaged with the Kelly rope 7, and the overwinding weight is attached to hang down from the top of the boom 2. When the winding spindle 14 is pushed up, the overwinding detector 2
8 is configured to operate. Similarly, an overwind detector (not shown) is attached to the auxiliary winding rope as well.

In such an earth drill equipped with an overload prevention device, the claws of the bucket 10 may get caught in the earth and sand when cutting the ground and hoisting the bucket at the end of excavation, and the hoisting operation may be difficult because the bucket 10 and earth and sand are in close contact with each other. However, when a large rope tension was applied, the overload prevention device was activated and the hoisting automatically stopped, making it impossible to perform a smooth hoisting operation.

For this reason, the hoisting operation of the bucket 10 was repeated by stopping the hoisting operation, rotating the bucket 10, breaking the contact between the bucket 10 and the soil, and then hoisting it again, which was said to be inefficient. There was a problem.

(Problems to be solved by the invention) In view of the above-mentioned problems, the present invention provides a grounding system that can improve work efficiency during excavation work and that does not reduce work safety during crane work. The purpose is to provide safety equipment for drills.

(Means for solving the problem) In order to achieve this purpose, the present invention provides a work state detection switch for detecting that the earth drill is in the excavation work state in an earth drill equipped with an overload prevention device for a crane. a timer that operates for a predetermined period of time while the excavation status is detected by the work status detection switch and after the excavation status ends; and an automatic stop prohibition switch that prohibits the overload prevention device from automatically stopping the hoisting direction operation signal of the control valve.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Figure 1 is an example of an electric circuit that realizes the automatic stop release mechanism due to overload of the present invention.
FIG. 2 is a diagram showing an example of a hoisting hydraulic circuit provided with the working state detection switch of the present invention, and FIG. 3 is a time chart for explaining the operation of the circuit shown in FIGS. 1 and 2.

To explain from the hoisting hydraulic circuit shown in Figure 2, 9
is the hoisting winch, which has a hoisting drum 9A rotated by the operation of a hydraulic motor 17.
15 is a hydraulic pump that drives the hydraulic motor 17, the hydraulic motor (not shown) of the Kelly drive device 5, the hydraulic cylinder 3 for hoisting the boom 2, etc., and 16 is a hydraulic pressure between the hydraulic pump 15 and the hydraulic motor 17. A control valve 18, which is a hydraulically operated three-position switching valve for the hydraulic motor 17 inserted into the circuit, is inserted into the hydraulic circuit between the control valve 16 and the hydraulic motor 17, and applies a holding pressure to the hydraulic motor 17. This is a counterbalance valve that holds suspended loads and performs braking when power is lowered.

21 is a pilot valve for switching the position of the control valve 16; 22 is a pilot valve for a hydraulic motor (not shown) for rotating the Kelly bar of the Kelly bar drive device 5; and a pilot circuit 37 on one side (hoisting side) of the control valve 16. An electromagnetic switching valve 23 that is switched by a signal from an overload prevention device (not shown) is inserted in the . Further, C is a circuit added according to the present invention, and includes a high pressure selection shuttle valve 24 provided between a pilot circuit 38 and 39 which is a secondary circuit of the pilot valve 22 of the Kelly bar rotation hydraulic motor, and It consists of a pressure switch 25 for detecting working conditions which is operated by pressure oil selected by a valve 24, and the pressure switch 25 is of a normally open contact type. 19 is a hydraulic pump that supplies pilot pressure oil to the pilot valves 21 and 22; 20 is a relief valve that sets the maximum discharge pressure; and 26 is an oil tank.

Next, to explain the electric circuit of FIG. 1, the overload prevention device 27 inputs each signal of the load detector 11, boom angle detector 12, and boom length detector 13 as described above, Perform the necessary calculations, compare the calculation results with the stored values, and if the result is an overload, perform hoisting, boom lowering, boom extension, etc.
This automatically stops dangerous movements in the event of a fall.

30 is a relay that is demagnetized by a signal from the overload prevention device 27, and 36 is its normally closed contact. 2
8 is a normally closed type micro switch that constitutes the above-mentioned overwinding detector, and the contact point opens when the Kerry bar 6, the winding hook, etc. are wound too much;
is a relay that is normally energized and deenergized when the microswitch 28 is activated, and 35 is its normally closed contact.

The parts surrounded by one-dot chain lines A and B are the parts added according to the present invention, 25 is a pressure switch for detecting the working state shown in FIG. 2, and 29 is a setting that is excited when the pressure switch 25 is closed. A variable or fixed timer, 33 is the timer 29
32 is a relay that is energized when the contact 33 closes, and 34 is a normally closed contact of the relay 32.

The normally closed contact 34 of the relay 32 is energized when the timer contact 33 closes, and the relay 30 is demagnetized by a signal from the overload prevention device 27.
The pilot circuit 3 of the control valve 16 shown in FIG.
The solenoid 23a of the electromagnetic switching valve 23 inserted into the solenoid 7 is connected to the solenoid 23a. Further, the normally closed contact 35 of the relay 31, which is demagnetized and energized by opening and closing of the overwinding detection micro switch 28, is connected in parallel to the series connection circuit of the normally closed contacts 36 and 34.

Next, the operation of the apparatus of this embodiment will be explained. First, earth drilling work will be explained in relation to the apparatus of the embodiment. The earth drilling work consists of four tasks: (1) grounding the bucket 10, (2) rotary excavation, (3) hoisting the bucket 10, and (4) discharging earth and sand. First, (1) grounding the bucket 10: Hoisting winch 9
Lower the bucket and ground the bucket 10 to the bottom of the excavation hole.
This lowering is performed by operating the pilot valve 21 in FIG.
Supply pilot pressure oil to b and control valve 1.
6 to position B, and the hydraulic motor 17 is lowered and rotated by the pressure oil from the hydraulic pump 15, or the clutch (not shown) is disengaged and the clutch is free-hauled.

Next, (2) rotary excavation is performed by operating the pilot valve 22 and switching the Kelly drive control valve (not shown) to rotate the hydraulic motor of the Kelly bar drive device 5, and transmitting the rotational force to the bucket via the Kelly bar 6. 10 and perform rotary excavation. When the bucket 10 is filled with earth and sand, the pilot valve 22 is reversely operated to rotate the bucket 10 in the opposite direction, thereby cutting the claws of the bucket 10 and the friction on the side walls of the bucket.

Next (3) To hoist the bucket, operate the pilot valve 21 to the hoisting side, and thereby the hydraulic pump 19
The oil from the pilot valve 21 acts on the pressure receiving part 16a of the control valve 16 through the A port, the electromagnetic switching valve 23 and the pilot circuit 37, and switches the control valve 16 to the A position, so the hydraulic motor 17 rotates in the hoisting direction. Kelly Rope 7
is wound up by the drum 9A, and the Kelly bar 6 and the bucket 10 are wound up. When the bucket 10 is hoisted up to an appropriate height above the ground, (4) earth and sand are discharged, and one cycle is completed. The present invention relates to the above-mentioned (3) winding, especially the bucket cut (the moment of winding).

In the circuit shown in FIG. 1, if there is no relay contact 34, which is the automatic stop prohibition switch according to the present invention, if the overload prevention device 27 is activated during winding, the relay 30 is demagnetized and its normally closed contact 36 is closed. Therefore, the electromagnetic switching valve 23 switches from the A position to the B position, and the pressure receiving part 16a of the control valve 16
becomes the tank pressure and hoisting stops. The boom lowering and boom extending operations are also automatically stopped by the same operation.

On the other hand, in the embodiment, when operating the pilot valve 22 shown in FIG. 2 to rotate the hydraulic motor of the Kelly bar drive device 5 in the forward or reverse direction, the hydraulic pressure in the pilot circuit 38 or 39 increases, so that the hydraulic pressure in the pilot circuit 38 or 39 increases. As shown, pressure switch 25 is closed.
Therefore, in FIG. 1, the timer 29 is energized and its instantaneous operation time-limited return contact 33 is closed, thereby energizing the relay 32.
The normally closed contact 34 of is opened. At this time, the overwinding detection microswitch 28 is closed, so the relay 31 is energized and its normally closed contact 35 is open. Therefore, even if the relay 30 is demagnetized by the signal from the overload prevention device 27 and its normally closed contact 36 is thereby closed, the electromagnetic switching valve 23
The solenoid 23a is not energized, so the electromagnetic switching valve 23 remains in the A position. Therefore, when the pilot valve 21 is operated to the hoisting side, the control valve 16 is held at the A position, and the winch 9 can generate force until the relief pressure is reached.

This automatic stop prohibition state is maintained for the off-delay setting time T of the timer 29 after the Kelly drive pilot valve 22 is returned to neutral and the excavation is completed.

That is, during excavation and for a predetermined period of time after the end of excavation (for example, about 30 seconds or 1 minute), the overload prevention device 2
7, automatic stop of winding is prohibited. Therefore, during ground cutting and hoisting after excavation, the maximum winch force, that is, the maximum capacity of the machine can be exerted, so that smooth hoisting can be performed.
Moreover, at this time, since the Kelly bar 6 and the bucket 10 are in the excavation hole, the machine will not fall.

In addition, as described above, the overwinding prevention relay 31
The contact 35 of the winding overload preventer 27 is connected in parallel to the series connection circuit of the contact 36 of the relay 30 demagnetized by the overload preventer 27 and the contact 34 of the relay 32 added according to the present invention. Even if automatic stop is prohibited, the overwinding prevention device operates normally, so when the Kerry bar 6 or the hook is overwound, the contact 35 closes, the solenoid switching valve 23 switches from the A position to the B position, and the control valve It is safe because the pressure receiving part 16a of 16 becomes the tank pressure, the hydraulic motor 17 of the hoisting winch 9 is stopped, and hoisting is stopped.

Furthermore, in this embodiment, the relay contact 34, which is the switch for inhibiting automatic stop, is also a normally closed contact, so if the timer 29 or its related circuit fails, the contact 34 closes, so the overload prevention device 27 The solenoid switching valve 23 is activated by the automatic stop signal from
is switched to position B and winding is automatically stopped, so it is safe.

Furthermore, the reason why the relay 32 is made to operate even during excavation is that if hoisting of the bucket 10 becomes impossible due to close contact between the bucket 10 and earth and sand, hoisting may be performed while rotating the bucket 10. It's for a reason.

In addition, since the prohibition of automatic hoisting stoppage by the overload prevention device 27 is limited to the time of excavation and a predetermined time after the completion of excavation, the automatic hoisting stop mechanism by the overload prevention device 27 operates normally when crane work is performed. Therefore, it is safe.

Although the above embodiments have been described with reference to the case where the boom 2 is a telescopic boom, the present invention can also be applied when the boom 2 is a non-retractable boom. Furthermore, each switch can also be configured by a semiconductor switch or the like. Further, the working state detection switch is not limited to the pressure switch 25 shown in the embodiment, but may be any switch that can detect the excavation state, for example, a pressure switch provided in the drive circuit for rotating the Kelly bar. Alternatively, it may be configured by a switch that detects the rotation of a hydraulic motor for rotating the Kelly bar or a rotating body rotated thereby, a switch that detects the movement of the operating lever of the pilot valve 22 for rotating the Kelly bar, or the like. Further, the present invention can be realized by a combined circuit including a switch that prohibits automatic stop during excavation work, and a timer that prohibits automatic stop for a certain period of time after the end of excavation.

(Effects of the invention) As described above, in the present invention, the automatic stop of hoisting by the overload prevention device is prohibited during earth drill excavation and for a predetermined period of time after the completion of excavation. Maximum winch force can be exerted during cutting, hoisting, etc., and smooth hoisting is possible.

In addition, the prohibition of automatic hoisting stoppage by the overload prevention device is limited to during excavation and a predetermined time after the completion of excavation, so when crane work is performed, the automatic hoisting stop mechanism by the overload prevention device operates normally. It's safe.

In addition, we have made it possible to prohibit the automatic stop of hoisting by the overload prevention device even during excavation, so if it becomes impossible to hoist the bucket due to close contact between the bucket and earth and sand, you can continue hoisting while rotating the bucket. I can do it.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram showing an embodiment of the safety device according to the present invention, Fig. 2 is a hydraulic circuit diagram of a hoisting circuit in the embodiment, Fig. 3 is a time chart for explaining the operation of the embodiment, and Fig. 4 is a hydraulic circuit diagram of the hoisting circuit in the embodiment. The figure is a side view of the earth drill.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In an earth drill equipped with an overload prevention device for a crane, a working state detection switch detects that the earth drill is in an excavation work state, and a work state detection switch that detects when the earth drill is in an excavation work state. a timer that operates for a predetermined period of time while the condition is detected and after the end of the excavation operation state;
and an automatic stop prohibition switch that is driven during the operating time of the timer and prohibits the overload prevention device from automatically stopping the hoisting direction operation signal of the control valve of the grounded drill's bucket hoisting winch. Drill safety device. 2. A request for registration of a utility model characterized in that the automatic stop prohibition switch is connected in series to a switch activated by an overload prevention device, and a switch activated by an overwind prevention device is connected in parallel to the series connection circuit. The safety device for the earth drill described in item 1. 3. The safety device for an earth drill according to claim 1, wherein the automatic stop prohibition switch is constituted by a normally closed contact of a relay.